The Babel Fish is a small, leech-like, yellow fish, and by putting this into one's ear one can instantly understand anything said in any language; this is how Arthur Dent is able to comprehend the other beings he encounters on his travels. The Babel fish has led to significant and profound consequences for the Universe; apart from the philosophical implications, the Babel fish has started more and bloodier wars than anything else in the history of creation, because it has removed all barriers to communication.